Three section telescoping crane boom



2 Sheets-Sheet 1 S. G. KNIGHT ETAL THREE SECTION TELESCOPING CRANE BOOMMarch 2, 1965 Filed Deo. 5, 1962 /J-Z 'y 'IEIOII 1615 t JZ 55 1 56 )Illl L', I "Y "I lll Il! Q s 10 jme/22%@ March 2, 1965 s. G. KNIGHT ETAL vTHREE SECTION TELESCOPING CRANE BOOM 2 sheets-sheet 2 Filed Deo. 5, 1962United States Patent Ohce artists Patented Mar. 2, 1965 3 171,545 THREESECTIN TEJESCOPING CRANE BOOM Sidney G. Knight and F V. Swanson, Wausau,Wis.,

assignors to Drott Manufacturing Corporation, Milwaukee, Wis., acorporation of Wisconsin Filed Dec. 3, 1962, Ser. No. 241,632 4 Claims.(Cl. 212-144) This invention relates to mobile cranes and moreparticularly -to a mast and extension boom structure for use with mobilecranes.

Mobile cranes in general comprise a Vehicle which supports an upwardlyextending mast having a boom pivoted thereto on a horizontal axis withmeans for swinging the boom vertically and a movable block at the end ofthe boom to pick up a load. The boom is preferably extensible to reachout and pick up loads at different distances from the vehicle.

One of the problems encountered with such cranes involves theconstruction of the mast and mounting of the boom and power operatingmeans thereon to swing the boom vertically without unduly complicatingthe structure or requiring an extra large vand expensive motor to swingthe boom. This problem also involves the matter of balancing the partsso that the maximum load can be raised by the crane without tilting themast or the vehicle.

Another problem is construction of lthe telescoping boom to provide thedesired strength in different extended positions thereof without makingthe boom structure unduly heavy. In this connection, it is noted that aboom of at least three sections is necessary to obtain the desireddegree of extension and of the three sections the base section is alwayslargest and strongest and the end section is always the smallest andweakest. It is also noted that the heaviest loads are picked upclose tothe vehicle. It is therefore desirable in extending the boom to move theintermediate and end sections out together as far as possible beforeextending the end section from the intermediate section in order toobtain maximum strength.

It is one of the objects of the present invention to provide a mobilecrane in which the mast and boom are so constructed and connected as toprovide the best possible balance and to enable the boom to be pivotedvertically to raise the maximum weight by the use of a relatively smallmotor which is easily and simply mounted to produce minimum interferencewith operation of the boom.

According to a feature of the invention, the mast is formed with ahorizontally elongated upper section to one end of which the boom ispivoted and angular intermediate and vertical lower sections with anextensible and contractible uid motor pivoted at one end to the boom andat its other end to the lower part of the mast to produce maximumlifting effect and minimum interference with the operating parts.

A further object is to provide an extensible boom for a mobile crane orthe like in which the end intermediate sections are latched togetheruntil the intermediate sec`- tion is fully extended from the basesec-tion and are then automatically released for extension of the endsection.

According to a feature of the invention the latch means comprises a pinprojecting laterally from the inner end of the end section through anopening at the inner end of the intermediate section and a cam carriedby the outer end of the base section to cam the pin out of the openingwhen the intermediate section approaches the limit of its outwardmovement in the base section.

The above and other objects and features of the invention will be morereadily apparent from the following description when read in connectionwit-h the accompanying drawings, in which:

FIG. 1 is a perspective view of a mobile crane embodying the invention;

FIG. 2 is a partial side view with parts broken away;

FIG. 3 is an enlarged side view of the extensible boom with parts brokenaway and in section;

FIG. 4 is a partial section on the line 4-4 of FIG. 3; and

FIG. 5 is a partial section on the line 5 5 of FIG. 3.

The mobile crane, as shown in FIG. l, includes a vehicle, indicatedgenerally at 10, which may be of the wheel or track laying type, butwhich is shown as being supported on wheels 11. The vehicle contains itsown source of motive power and may be driven from place to place by anoperator housed in a cab 12. In addition to controlling the vehicle, theoperator may also control operation of the crane structure.

The crane structure comprises a mast which is rotatably mounted in arotatable support 13 on the vehicle for turning about a vertical axis.The mast as shown comprises a lower vertical portion 14 mounted on thesupport 13, an intermediate portion 15 lying at an acute angle to thevertical and an upper horizontal portion 16. The several portions of themast may be fabricated of steel plates secured together in asubstantially channel section structure, as best seen in FIG. l, forconvenient mounting of t-he boom therein.

A boom, indicated generally at 17, is pivoted at one end to the free endof the horizontal mast portion 16 on an axis indicated at 1S. In itslowered position the boom may lie between the sides of the horizontalchannel section 16 of the mast, as seen in FIG. l, and may be swungupwardly about the pivotal connection 18, as illustrated in FIG. 2. Forcontrolling the mast an extensible and contractible hydraulic motorcomprising a cylinder 19 and a piston having a piston rod 21 projectingfrom one end thereof is pivotally connected to the mast and to the boom.As shown, the end of the piston rod 21 is pivoted at 22 to a point onthe mast spaced from the pivotal axis 18 and preferably lying adjacentthe opposite end of the horizontal mast portion 16. The end of thecylinder is pivoted at 23 in the lower vertical portion of the mast sothat the cylinder and piston mechanism lie substantially between thesides of the channel shaped intermediate mast portion I5. In thislocation, the cylinder and piston mechanism is protected by the mast andoccupies a minimum amount of space. The motor is also positioned so thatits angle of action on the boom is favorable in all pivoted positions ofthe boom so that a motor of minimum size may be used to control verticalswinging movement of the boom.

The boom, as best seen in FIGS. 3 to 5, is formed of three tubularsections which telescopically intert with each other and which arepreferably, although not necessarily, rectangular in section. The threesections comprise a base section 24, an intermediate section 25 and anend section 26. The base section carries a bracket 2'7 at its inner endthrough which it is pivoted on the mast. Intermediate its ends the basesection carries a winch mechanism comprising a rotatable drum 28enclosed within a housing 29 secured to the base section. The drum 28may be driven through any desired type of motor as, for example, ahydraulically operated motor 31 as shown in FIG. 2, which is suppliedwith operating liquid under pressure under the control of the craneoperator.

The intermediate section is of a size to slide fully into orsubstantially out of the outer end of the base section, suitable slidingbearing members not shown being provided to facilitate this slidingmovement. The end section 26 is similarly slidably tted into theintermediate section. The end section carries at its outer end a blockand tackle mechanism for lifting a load, although it will be understoodthat any other desired type of load engaging Vthe boom. Since the basesection is-the largest` and cor-v 70 and lifting means could besubstituted.'v As shown, a head the sheave 33 and over a sheave in ablockY 35 which may carry a load engaging hook 36. The cable .thenVpasses over the otherrsection of .thedouble sheave 33 andoack l Ito ananchor point on the block, as illustrated. With this construction whenthe drum 28 is rotated in one direction 'or the other the cable will bewound onto or unwound from `the drum to vcause the block 35"to be raisedvand lowered, as will be understood. Y l

According to the present invention, the endand intermediate sections ofthe boom are latched together against relaitve movement during initialextension of boom and until .the intermediate section has reachedsubstantially the full limit of its movement Voutward fromthe basesection. As best seen in FlG. 4, the latch comprises a sleeve 37 securedto the inner end of the end section 26 and slidably carrying a pair oflatching pins 38 which are adapted to project from opposite ends of thesleeve and which are urged apart by a `compression spring 39. When theend section is fully retracted into the intermediate section, the latchpins 38 will extend through latching openings 41 formed in the sideWalls of the intermediate section. Preferably the openings 41 are aredat their ends, as shown, and the latch pins have tapered ends, as shown,so that -when the latch pins are moved to a position with their outerends llush or substantially ush with the outer surface of theintermediate section, they will be cammed inwardly yto their fullreleased position by exertion of longitudinal pressure thereon.

In order to release the latch pins so that the end section can beextended from the intermediate section, cam

means are provided as best seen in FIG. 5. Each ofthe' lcam means, asshown, comprises a wedge-shaped plate member 42 pivoted at one end,V asshown at 43, on a bracket extending outward from the base Section 24.

The other end of the cam member is adapted to .be adjustably secured tothe base section by an adjusting screw `44. When the cam plate isproperly adjusted its 'inner surface will taper inwardly of the basesectionfrom a point flush with the inner surface .o-f the base sectionadjacent to the pivot 43 to a Vpoint substantially flush with the inner`surfaces ofthe intermediate-section 25 adjacent to the adjusting screw44. The cam plate may, if desired, be provided with a wear stripy at itsrtip which can easily be replaced in the event of wear. The boom isadaptedto be extended and retracted vby power means controllable by theoperator from the cab. 12 of the crane. In the preferred form shown, thepower means comprises an extensible and rectractable fluid motor,including a cylinder 45 pivoted at oneV end to a bracket 46 carried bythe inner end of the basesection. A piston in the cylinder has itspiston rod extending from the opposite end thereof and connected to theouter end of the end section of the boom, as shown at 47. When the iluidmotor is extended the boom will 'be extended correspondingly and whenthe fluid motor is retracted it will telescope the Vintermediate and endsections of the boom into the base section to provide the minimum lboomlength. Y l

During extension of thel boom, the latch pins 38 will 'initially beengaged lin thel latching openings 41 to hold the intermediate and endsection against movement relative to each other. Thus during the`initial extension, the'v intermediate and end'sections will movetogether and will reinforce each other to provide Afory maximumystrength rof respondingly strongest of the several sections, this feaorsubstantially ush with the outer Surfaces .-of the intermediate section.Whena further extending force is exerted on the endsection bythe uidmotor, .the latch pins willl be cammedinwardly due to the shapeof ,theirends and tothe lshape of the-openings 41 to slide against the innersurface of theV intermediate section.l At this time, -the boom canbe'exended to its maximum reach with the end section telescoping out,of'the intermediate section. Upon retraction of the boom, the latch pinwill re-engage in the latching openings, the operation being entirelyautomaticand without any attention from the operator. i

While one embodiment of the invention has been shown and describedherein, it will be understood that it is illustrative only and not to betaken as a definition of the scope of the invention, reference being hadfor .this purpose ot the appended claims. y

What is claimed is:

l. In a mobile crane, an extensible boom comprising a tubular basesection, a tubular intermediate section telescopically slidable in thebase section, an end section telescopically slidable lengthwise in theintermediate vsection, latch means releasable holding the intermediateand end sections against relative sliding movement, means Acarried bythe base section to engage and release the latch means when theintermediate section has reached substantially the limit of `its outwardmovement in the base section, Vand power means engaging .the basev andend sections toV extend and retract the boom.

2. The construction of claim 1 in which the end section is tubularandthe power means is an extensible hydraulic kinner end toprojectthrough said opening when theboom is retracted thereby to hold the endand` intermediate sections against relative sliding movement, cammeanswcarried by the base section adjacent to itsV outer end to cngagethe latch pin and cam itvv radially inward out of said opening when thevintermediate section is at substantially the limit of its outwardmovement in the base section,

fand -power means connected to the base and end sections to expand vandretract theboom.

4. The construction of yclaim 3 in which the end section is tubular andthe power means is an extensible and contractable uid motor Vlying inthe'end section when the boom is retracted.

References Cited by the Examiner UNITED STATES PATENTS 1/57 Boysen et al212-145 2,787,383 4/57 Antos et al 212-55 X 2,819,803 V`1/58r Obenchain212-55 SAMUEL FLCOLEMAN, Acting Primary Examiner.

' J, ALBRECHT, Examiner.

1. IN A MOBILE CRANE, AN EXTENSIBLE BOOM COMPRISING A TUBULAR BASESECTION, A TUBULAR INTERMEDIATE SECTION TELESCOPICALLY SLIDABLE IN THEBASE SECTION, AN END SECTION TELESCOPICALL SLIDABLE LENGTHWISE IN THEINTERMEDIATE SECTION, LATCH MEANS RELEASABLE HOLDING THE INTERMEDIATEAND END SECTIONS AGAINST RELATIVE SLIDING MOVEMENT, MEANS CARRIED BY THEBASE SECTION TO ENGAGE AND RELEASE THE LATCH MEANS WHEN THE INTERMEDIATESECTION HAS REACHED SUBSTANTIALLY THE LIMIT OF ITS OUTWARD MOVEMENT INTHE BASE SECTION, AND POWER MEANS ENGAGING THE BASE AND END SECTIONS TOEXTEND AND RETRACT THE BOOM.